Many safety systems operate on the principal of first determining what type of object is within a region then potentially disabling some device after the determination. For example, many systems within the infrared safety domain utilize techniques that combine images then analyze the combined image via pixel spectral power, density and/or threshold values. Other techniques include measuring thermal properties; measuring moving surfaces (reflectivity, smoothness, and so forth.); and techniques utilized to determine position. The following provides a brief description and examples of some current implementations that employ one or more of the above techniques.
One example includes a remote sensing system for real time monitoring of patient position which can report variations in patient setup from day to day as well as motion during individual treatments. In particular, this type system includes: (a) a source of radiation for applying radiation to a patient; (b) targets affixed to the patient for reflecting radiation impinging thereon; (c) two cameras and a computer for detecting the reflected radiation and for determining the current position of the targets in three-dimensional space; (d) a data store for storing the position of the targets; (e) the computer also serving to compare the current position of the targets with positions stored in the data store; and (f) a display for displaying indicators whenever differences between the current position and the stored position exceed tolerances stored in the data store. This type of system employs reflected radiation for determining the position of a person.
Another example includes a system for detecting presence and/or motion of a person or other movable entity within a selected space. Detection is accomplished by detecting reflected light or other radiation from the space, presence being signified when detected radiation differs from an established background, either up or down, by an amount exceeding a predetermined threshold. Blending of the entity with the background is avoided by viewing the entity at least two different angles with different backgrounds, for example by use of two spaced detectors, and variations in background are automatically compensated for when a presence indication persists for a selected period of time after the last motion indication is received. The background is updated to the current level when this occurs. With light radiation, light sources are structured to irradiate substantially the entire space and saturation of a detector by ambient radiation is avoided by providing a band-pass filter which passes only radiation in a narrow overlap wavelength band for the radiation sources and detectors. This type system operates by analyzing reflected radiation from the space, wherein differences in the reflected radiation are detected.
In yet another example, a system includes an infrared detector having two cameras for viewing a scene to detect humans. The cameras focus the scene on respective pixel arrays. One array is designed with a filter to be sensitive to light from 0.8 to 1.4 microns and the array of the other camera is designed with a filter to be sensitive from 1.4 microns to 2.2 microns. The arrays are co-registered spacially and temporally relative to the viewed scene and pixel transmission dynamics. The spectral powers of the pixels from both arrays are difference weighted and fused into one set of pixels. The fused pixels are thresholded into another set of pixels that have one of two values—black or white. These pixels are entered into a visual display that shows a segment image of a human if in the viewed scene. This type system employs image processing techniques that analyzes spectral densities associated with pixels.
Another system includes a camera arrangement for detecting an object such as a driver or a child seat located on, above or in front of a vehicle seat. The system includes a camera for creating an image of any object in that position, and also includes an electromagnetic wave source such as an infrared light source. An image created with the source operational is stored in a first store and an image created with the source non-operational is stored in a second store. The stored images are then subtracted and any object in the subtraction image is identified by an image processor. The position of the object may also be determined and used to inhibit or modify the operation of a safety device such as an airbag in the vehicle. This type of system identifies an object by digital subtraction of images taken before and after illumination by a source.
Although the above systems serve various applications, these systems suffer in that reflected radiation from the object must first be received by a detector and then post processed in order to make a determination or identification regarding the object. These types of analyses can be prone to error depending on the reflectivity of the object, speed of the object, and other factors associated with object variables.